Speed Gains f0r 2011: What did you do?

[Ratickle]

Smarty ,,we added a Bussell to the transom ,to reduce the vacume at the back of the boat,,,i useto have a real tall scoop ( about 14'' high) ,,and as you can see ,i went to the hydro ,cabover 5'' ,,their are also a hand few of things ,i,v done to the deck and hull that will come out after everyone sees it at the first race,,SARASOTA !!

So now I have to figure out how to make sure I get to Sarasota just so I can see your boat??????

Naw, just so I can see everyone and their boats.....:sifone:

 

[imco offshore]

come on down Paul ,,we will have a great time ,,and i,m sure after a few beers ,,a great svl race will break out,, southweast air ,,,and LaQuinta ,,are ready ,,

 

[Griswald]

thanks Gris,,,i,m dying to come out to Texas with her ,when you guys have the big tie-up party,,,:cheers2::cheers2::cheers2:

Every weekend...

I'd love to see the IMCO boat cruising up the lake. Would turn some heads for sure. Might give my Fever a run! :driving:

 

[Smarty]

Smarty ,,we added a Bussell to the transom ,to reduce the vacume at the back of the boat,,,i useto have a real tall scoop ( about 14'' high) ,,and as you can see ,i went to the hydro ,cabover 5'' ,,their are also a hand few of things ,i,v done to the deck and hull that will come out after everyone sees it at the first race,,SARASOTA !!

Thank you the reply, I do appreciate it. What do you think you gained by the reduced aero-drag? I remember when Fountain started rounding the deck near the transom of his 40'/42' raceboats years ago. I was always wondering what really worked, how much faster it went as compared to the previous design. I am like a sponge when it comes to learning new perfromance improvements for boats, and I like to learn, even at 46 years of age.

I thought the bussel was mostly cosmetic, sio if in fact it reduces drag and increases top speed, I have learned something new today, and now appreciate the bussel much more than I previous did. Thanks again.

Stephen

 

[htrdlncn]

I would imagine as boats get faster and faster as much attention will have to be paid to aerodynamics as is paid to hydrodynamics

 

[imco offshore]

Stephen ,,it would be hard to put a number on the bussell ,,what i,m trying to do is free up the boat ,by reducing the drag pockets ,,and in turn gain handeling responce,,which i hope will improve overall lap times,,,,their are a few hot spots on the hull and deck ,with an extreme amount of pressure at speed ,,so i have reduced ,,or even eleminated them ,by either ,,a vacume or pressure defuser application,,, i,ll try to keep you informed on how they work as i test next week some more ,,, hope this makes sense,,
,in racing ,,you either " follow and complain " or " lead and keep working "

 

[Slandrew]

Heads exaust no real speed gain but I have to put the good props on we'll see?

 

[osur866]

That is great. I had an 18' Donzi, loved the boat. There used to be a blue X18 Donzi with a SBC blown and arneson drive that ran strong (over 100 mph), never met the owner who put it together (George Desomd), but alwasy thought of making an 18' Donzi ran anywhere 80 mph is ballsy, and a cool boat. I like what you are doing with your boat!

Keep us informed on how the prop testing goes. Cool performance upgrade.

Still prop testing, still need to bring down the RPM's about 300 more which should get me another 4-5 I'd think

 

[imco offshore]

what drive system are you running those rpms thru ?

 

[Ratickle]

Still prop testing, still need to bring down the RPM's about 300 more which should get me another 4-5 I'd think

what drive system are you running those rpms thru ?

Holy Crap Batman......

 

[osur866]

what drive system are you running those rpms thru ?

Here comes the comments but, it's a newer style swept back stock Bravo 1 with -2" Imco lower, oh and the upper is 1.65 geared, RPM's are in the 5,800 neighborhood, however I'm running 3 bladed props, slip #'s are in the 7.7-8% range

Steve

 

[imco offshore]

thats awsome ,,good job ,,please let us know the final #.s ,,i,m always open and looking for the new next speed moves,,thanks George Jr.

 

[osur866]

George,

Couple things to take into account here, 1st its a 3200 lb boat running a pretty deep propshaft height (5 1/2") even with the -2", it's been the opinion of some that spinning a larger prop slower is more efficent than turning a smaller prop faster, I do believe this to account for my pretty low slip #'s with running the 3 blades, hence why I'm trying to stay with the 1.65 upper gears, could the boat benefit from a -3" lower and possibly a extension box? Yes I think it could, but then again just how fast does one need to go in an 18' boat anyway??


Steve

 

[Slandrew]

George,

Couple things to take into account here, 1st its a 3200 lb boat running a pretty deep propshaft height (5 1/2") even with the -2", it's been the opinion of some that spinning a larger prop slower is more efficent than turning a smaller prop faster, I do believe this to account for my pretty low slip #'s with running the 3 blades, hence why I'm trying to stay with the 1.65 upper gears, could the boat benefit from a -3" lower and possibly a extension box? Yes I think it could, but then again just how fast does one need to go in an 18' boat anyway??


Steve

At the lower R$PM is the boat more or less stable to the water?Nice boat&speeds!:USA:

 

[imco offshore]

man what a great looking set-up,,,i agree with the 3 and 4 blade for top end speed ,,i would do the same for kilo runs in my boat ,,, but in racing i need to accelerate to turn one and off each corner ,,thats why i stayed with 6 blades ,,while most turned 5,,
I have an 18 CHAMP which i,m going to start to restore in the next few months,,it looks like i,ll smallblock it with an IMCO ,, i like the 1.65 gears your running ,,might copy !

 

[osur866]

At the lower R$PM is the boat more or less stable to the water?Nice boat&speeds!:USA:

Don't exactly understand your question, but is the boat stable? That's all relative, it's defiantly a drivers boat, if you just sit in the drivers seat and do nothing but give it throttle and a lil trim then yeah she's gonna get your attention real quick!! Yes it has a tendency to chine walk if you let it, starting in the low-upper 70's and is pretty soild into the low 80's it can be controlled by counter steering, at wot I don't use any tabs they are high and dry and it doesn't require much trim not more than 1/4 for best speed, but im using 3 blade bow lifting props, boat DOES NOT like 4 blade props too much stern lift which makes it pretty loose! Keep in mind it's a 24* bottom but it does have a rounded keel, so the higher the stern rides the more it wants to chine walk and it really becomes a balancing act to keep the rounded keel from falling from one side to another which induces the chine walk. 4 blades and over trimming all have a great effect on it, it's very sensitive to trim/tab input!

But no it's not as stable as a 30 something twin when running at same speeds up to 70 it's rock soild anything after is when you need to be on your game and really driving the boat!

George with the 1.65's the acceleration will be much better than a 1.5 gear.

What kinda power are considering for your champ? If your keeping it below 400 I'd consider finding an Alpha SS they are shorter with less hydro drag account a much smaller case some of the other Donzi guys with 16/18's have had great success with those.

Steve

 

[Traviss]

Didnt have to do much this year, gonna try new prop and did drop a few pounds of my hefty azz LOL! last gps was 88. laser prop wouldnt hold anymore. Raised X 2" since then. Should be over 90 if I can find that money tree to get sum fuel :huh:

 

[Slandrew]

Don't exactly understand your question, but is the boat stable? That's all relative, it's defiantly a drivers boat, if you just sit in the drivers seat and do nothing but give it throttle and a lil trim then yeah she's gonna get your attention real quick!! Yes it has a tendency to chine walk if you let it, starting in the low-upper 70's and is pretty soild into the low 80's it can be controlled by counter steering, at wot I don't use any tabs they are high and dry and it doesn't require much trim not more than 1/4 for best speed, but im using 3 blade bow lifting props, boat DOES NOT like 4 blade props too much stern lift which makes it pretty loose! Keep in mind it's a 24* bottom but it does have a rounded keel, so the higher the stern rides the more it wants to chine walk and it really becomes a balancing act to keep the rounded keel from falling from one side to another which induces the chine walk. 4 blades and over trimming all have a great effect on it, it's very sensitive to trim/tab input!

But no it's not as stable as a 30 something twin when running at same speeds up to 70 it's rock soild anything after is when you need to be on your game and really driving the boat!

George with the 1.65's the acceleration will be much better than a 1.5 gear.

What kinda power are considering for your champ? If your keeping it below 400 I'd consider finding an Alpha SS they are shorter with less hydro drag account a much smaller case some of the other Donzi guys with 16/18's have had great success with those.

Steve

Thanks!I over propped in a boat comparible to yours while a got 1 more mile an hour she chine walked more but that was my question!Again nice ride&speeds!

 

[Smarty]

George,

Couple things to take into account here, 1st its a 3200 lb boat running a pretty deep propshaft height (5 1/2") even with the -2", it's been the opinion of some that spinning a larger prop slower is more efficent than turning a smaller prop faster, I do believe this to account for my pretty low slip #'s with running the 3 blades, hence why I'm trying to stay with the 1.65 upper gears, could the boat benefit from a -3" lower and possibly a extension box? Yes I think it could, but then again just how fast does one need to go in an 18' boat anyway??


Steve

That is great! Keep up the testing, it seems to me based on all your posts you definitely are getting the Donzi dialed-in. I like what I see.